(a) Field of the Invention
The present invention relates to a punched electrode and a lithium secondary battery using the same, and more particularly to a punched electrode that can improve cycle life, capacity, and safety characteristics of batteries, and a rechargeable lithium secondary battery using the same.
(b) Description of the Related Art
Recently, an explosive increase in demand for portable electronic equipment has also made the demand for secondary batteries rapidly increase, and in particular, the role of lithium secondary batteries has been very important therein. In addition, as portable electronic equipment has been miniaturized and the efficiency thereof has been heightened, high performance, miniaturization, and various shapes of batteries have been required. Particularly, for personal computers, various shapes of batteries to decrease the thickness of personal computers have been attempted because battery size has a large influence on thickness of a personal computer. In addition, as serious environmental problems have arisen, solutions to global warming have been seriously and continuously discussed.
For a solution to these problems, legislation to decrease use of automotive petroleum fuel, which is a principal cause of global warming, and obligations to use electronic vehicles that are more environmentally friendly have been discussed, and some such directives are currently in force. In addition, in order to solve pollution problems, studies and development of electronic vehicles (HEV, EV) have been continuously carried out, and some such vehicles are commonly used now. For this, batteries having large capacity are required, and a novel approach to thermal stability and safety is also required.
In order to satisfy these needs, an attempt to increase height and width of batteries has been made. Although such an attempt can increase battery capacity and simplify the shape of batteries, it may be an obstacle to battery performance because there are difficulties in uniformly wetting the entire electrode area with electrolyte as the electrode area widens, and in causing a uniform electrode reaction over the entire electrode area during progression through charge and discharge cycles. Therefore, although electrode conditions are fair, a lack of electrolyte may accelerate electrode degeneration and therefore shorten the cycle life of batteries. In addition, if an electrode becomes seriously non-uniform, electrode reactions will be locally concentrated, and local deposition of lithium metal may cause safety problems.